The song played by the Japanese toilet is "Days of Blues" by Sons of Maria, a Swiss electronic music duo. The song is widely available to license from stock music providers.
In the final scene with the camera facing the Marsh family, there is a wall decoration with three horseshoes on it. This could be a nod to the film Demolition Man (1993), which is set in a future people don't use toilet rolls, instead they use the three seashells.